The invention relates to an instrument system for minimally-invasive surgery.
Minimally-invasive interventions are assuming an increasingly great importance in the field of clinical surgery. While just a few years ago relatively large areas of the site were opened up for small surgical interventions, to make it possible for the surgeon to navigate through natural landmarks, it can be observed that a plurality of these interventions are nowadays carried out by means of laparoscopy and optical support in the form of endoscopy. This trend is likely to continue, aided by the direct advantages of minimally-invasive interventions. Endoscopes, laparoscopes etc. are referred to below by the general term endoscopic instruments, which are generally brought by a trocar placed into the inside of the patient. Instruments and trocar together form an instrument system.
Tele-operated robotic assistance systems are also known as instrument systems in which the surgeon enters movements at a console. The movement entries are then transmitted, scaled via a suitable kinematics system, to the instruments located in the body of the patient. Trocars are also used as a rule for this purpose. In other words a robot arm carries an instrument, wherein the robot arm in its turn is remotely controlled by the surgeon. The said robot assistance systems are playing a decisive role in systems currently being developed for the market.
There are numerous possible solutions for the design of the kinematics of said assistance systems. The instruments used are generally rigid. Their movements are effected by a robot arm located outside the patient. Previously a disruptively large space requirement has been necessary for this.
Newer concepts are also conceivable, which counteract this disadvantage. In accordance with said concepts the instruments themselves are equipped with ever greater degrees of freedom of movement. Many movements of the instruments then take place within the patient's body. Such movements no longer have to be actuated by the robot assistance system outside the body. The work space required for the robot outside the body thus remains restricted. The majority of the operational movements are thus implemented by kinematics with multiple degrees of freedom within the site.
A challenge now arises with these approaches in realizing a plurality of degrees of freedom for instrument movement with a small instrument diameter, to enable the instrument to be placed with a suitable trocar diameter. Such a diameter lies for example in the range of less than 10 mm. It is conceivable for example to drive the axes of the instrument's degrees of freedom primarily by cable constructions instead of by an electrically operated actuator, so that the instrument remains a low-cost instrument. This is designed to provide a disposable concept.
Disadvantageously at least two cables must be fed through the instrument structure for each degree of freedom of movement, to enable two directions of movement to be realized for the particular applied force or applied torque. This already results, for an instrument of which the movements cover the six degrees of freedom of the space, in the use of twelve cables at the most unfavorable point. Even if the first of the six axes is driven directly outside the patient, a functionality is generally also required for a work head of the instrument, i.e. an end effector. E.g. if a gripper is to be able to be actuated at the instrument tip, two cables are then additionally required for this purpose. These too must be routed through the instrument structure.
FIG. 3 shows a schematic of a section of a conceivable instrument 20, containing a support arm 22 and a work head 24 attached to the end thereof. An actuator 38 on the work head 24 in the form of scissors is operated via control lines 32 in the form of cables. The actuation represents a first degree of freedom. The work head 24 is also able to be rotated in relation to the support arm 22, which represents a second degree of freedom or a second actuator 38. This too is operated via two control lines 32 in the form of cables. The support arm 22 has rigid arm segments 100 which are connected to each other via a joint 102. Thus the joint 102 also represents an actuator 38, which is likewise moved via two control lines 32 or cables respectively.
FIG. 3 shows the realization of an instrument of 8 mm in diameter, on the basis of which an idea of the complexity of such a structure is given. FIG. 3 shows the complexity of the structure for three degrees of freedom. The expansion to more than five to six degrees of freedom with the same or even a smaller diameter is very probably no longer able to be implemented.